Up to date, a method of chemical processing of living tissue using a fixing agent such as glutaraldehyde or a method of removing cellular components from living tissue have been widely applied and found clinical application as methods of preparing a graft for transplantation into an animal.
It has been estimated for example that there are in excess of one million patients worldwide requiring a corneal graft. However as a result of a shortage of available eye balls in many countries, the number of patients undergoing corneal transplants annually is only about 60,000 persons. In Japan, in contrast to approximately 5000 wait-listed transplant candidates registered with the Japan Eye Bank Association, the number of eye donors is approximately 1000 and the number of usable eye balls is approximately 1500.
Moreover, since current corneal transplantation therapies employ allogeneic transplantation of the cornea of another person, there are problems associated with rejection reactions depending on the underlying disease. In this context, the development of an artificial cornea is expected to provide a radical solution to the above problems.
Synthetic polymers such as polymethylmethacrylate (PMMA), polytetrafluoroethylene (PTFE) and polyvinylalcohol (PVA) have been tested as materials for an artificial cornea. However the low compatibility between these materials and corneal tissue sometimes results in detachment or infection at the junction site of the artificial cornea and the corneal tissue.
Techniques of improving compatibility with living tissue have been developed in recent years by using a graft of decellularized tissue as a residual supporting tissue after removal of cells from living tissue. This decellularized tissue displays excellent compatibility with living tissue when compared with synthetic polymers as a result of physical properties which resemble living tissue.
Current cell depletion methods include chemical methods applying a chemical solution containing a surfactant or a proteolytic enzyme to living tissue or ultrahigh pressure treatment applying ultrahigh pressure of more than 5000 atmospheres to living tissue in water (refer to Patent Document 1). The latter method is used to solve problems associated with the former method such as the fact that infection is not always prevented and chemicals must be removed after transplantation.
Patent Document 1: Pamphlet of WO2004/24170.